Fragmentation can make seedlings wimpy

January 24, 2002

New research shows that fragmentation of tropical forests can make trees wimpy. Seeds from isolated trees had less genetic diversity and were less likely to germinate, and the seedlings that did grow had smaller leaves. This is the first study of how forest fragmentation affects seedling quality.

"Fragmentation of tropical dry forests reduces genetic variation and seedling vigor of the tree Samanea saman," says Mauricio Quesada of the Universidad Nacional Autonoma de Mexico's Institute of Ecology in Morelia, Mexico, who did this research with three co-authors in the February issue of Conservation Biology.

Tropical dry forest is one of the most endangered ecosystems in the world: more than 99% of the dry forest has been logged or converted to agriculture in tropical Mexico and Central America. Tropical trees are particularly vulnerable to fragmentation in part because they grow at low densities and depend on animals for pollination.

Quesada and his colleagues studied how fragmentation of a dry forest in northwestern Costa Rica affects a tree in the mimosa family (Samanea saman). The researchers compared isolated S. saman trees with those in continuous populations (the isolated trees were about a third a mile apart and were surrounded by agricultural fields, pastures or remnant forest patches; the trees in continuous populations were at about 4/acre and were surrounded by undisturbed forest. The researchers evaluated factors including seed production, relatedness and germination.

Quesada and his colleagues found that fragmentation decreased the vigor of S. saman seeds and seedlings. For instance, seeds from isolated trees were 15% less likely to germinate (58% vs. 75%) and the leaves of those that did sprout were 10% smaller (about 9 vs. 10 square inches).

Fragmentation also decreased genetic diversity: in isolated trees, seeds from different fruits of the same tree were four times more likely to have the same father. S. saman is thought to be pollinated by moths, and researchers speculate that fragmentation may keep the moths from visiting enough paternal trees to maintain genetic diversity levels.

The deleterious effects of fragmentation notwithstanding, Quesada and his colleagues caution that "trees in isolation or small populations should not be considered the 'living dead'." Several isolated trees had high levels of genetic diversity and so could serve as important "stepping stones" for the pollinating moths -- and thus gene flow -- between S. saman populations.
-end-
Quesada's co-authors are: Alfredo Cascante, Jorge Lobo and Eric Fuchs, all of the Universidad de Costa Rica in San Jose, Costa Rica. For copies of papers, contact Robin Meadows: robin@nasw.org. Please mention Conservation Biology as the source of these items.

Society for Conservation Biology

Related Genetic Diversity Articles from Brightsurf:

In the Cerrado, topography explains the genetic diversity of amphibians more than land cover
Study shows that a tree frog endemic to a mountainous region of the Brazilian savanna is unable to disperse and find genetically closer mates when the terrain is rugged, potentially endangering survival of the species

New DNA sequencing technique may help unravel genetic diversity of cancer tumors
Understanding the genetic diversity of individual cells within a cancer tumor and how that might impact the disease progression has remained a challenge, due to the current limitations of genomic sequencing.

Researchers uncover the arks of genetic diversity in terrestrial mammals
Mapping the distribution of life on Earth, from genes to species to ecosystems, is essential in informing conservation policies and protecting biodiversity.

Seahorse and pipefish study by CCNY opens window to marine genetic diversity May 08, 2020
The direction of ocean currents can determine the direction of gene flow in rafting species, but this depends on species traits that allow for rafting propensity.

Study helps arboreta, botanical gardens meet genetic diversity conservation goals
In a groundbreaking study, an international team of 21 scientists evaluated five genera spanning the plant tree of life (Hibiscus, Magnolia, Pseudophoenix, Quercus and Zamia) to understand how much genetic diversity currently exists in collections in botanical gardens and arboreta worldwide.

Study reveals rich genetic diversity of Vietnam
In a new paper, Dang Liu, Mark Stoneking and colleagues have analyzed newly generated genome-wide SNP data for the Kinh and 21 additional ethnic groups in Vietnam, encompassing all five major language families in MSEA, along with previously published data from nearby populations and ancient samples.

Coastal pollution reduces genetic diversity of corals, reef resilience
A new study by researchers at the University of Hawai'i at Mānoa School of Ocean and Earth Science and Technology found that human-induced environmental stressors have a large effect on the genetic composition of coral reef populations in Hawai'i.

New world map of fish genetic diversity
An international research team from ETH Zurich and French universities has studied genetic diversity among fish around the world for the first time.

Texas A&M study reveals domestic horse breed has third-lowest genetic diversity
A new study by Dr. Gus Cothran, professor emeritus at the Texas A&M School of Veterinary Medicine & Biomedical Sciences, has found that the Cleveland Bay horse breed has the third-lowest genetic variation level of domestic horses, ranking above only the notoriously inbred Friesian and Clydesdale breeds.

Genetic diversity facilitates cancer therapy
Cancer patients with more different HLA genes respond better to treatment.

Read More: Genetic Diversity News and Genetic Diversity Current Events
Brightsurf.com is a participant in the Amazon Services LLC Associates Program, an affiliate advertising program designed to provide a means for sites to earn advertising fees by advertising and linking to Amazon.com.